In addition to cleaning, another highly desirable characteristic of personal cleanser/shower gel type compositions is to deliver consumer perceivable (e.g., sensory or visual) benefits from the compositions to the skin. One important way of achieving this result is through deposition of benefit agent (e.g., emollient oils and/or of surfactant-insoluble inorganic particles). In turn, this may require incorporation of high levels of such oil or inorganic particles into the cleanser/shower gel composition.
Unfortunately, such dual cleansing and moisturizing compositions are difficult to formulate because cleansing ingredients, in general, tend to be incompatible with moisturizing ingredients. For example, emulsified oil droplets, especially hydrocarbon oil droplets, tend to phase separate from liquids during storage and to form a separate layer at the top of the liquid cleanser.
Also, emollient oils often tend to depress foaming/lathering of cleansing ingredients, especially when the level of surfactants in the liquid cleanser is relatively low (e.g., below about 25% by wt.). However, liquid cleansers containing relatively low level of surfactants and having good lather properties are highly desired because the lower surfactant levels tend to make the composition more mild, to lower cost and to facilitate processing.
Accordingly, there is a need in the art for compositions which contain low level of cleansing ingredients, which are both mild and capable of producing abundant lather, and which also can deliver moisturizing or other active ingredients. In addition, such compositions should stay physically stable at both ambient and elevated storage temperature.
Liquid cleansers, which can deliver skin benefit agents to provide some kind of skin benefit, are known in the art. For example, one method of enhancing delivery of benefit agent to the skin or hair is using cationic polymers such as Polymer JR® from Amerchol or Jaguar® from Rhone Poulenc. This method is disclosed, for example, in U.S. Pat. No. 3,580,853 to Parran et al, U.S. Pat. No. 5,085,857 to Reid et al., U.S. Pat. No. 5,439,682 to Wivell et al; or in WO 94/03152 (assigned to Unilever), WO 92/18100 (assigned to Procter & Gamble) or WO 97/48378 (assigned to Procter & Gamble).
Another method of enhancing delivery of benefit agents to the skin or hair is using large droplets of viscous oils as is described in U.S. Pat. No. 5,661,189 to Grieveson (assigned to Unilever) and U.S. Pat. No. 5,854,293 (assigned to Procter & Gamble).
In addition, the art discloses that physical stability of, for example, an emollient oil cleanser system requires the presence of some sort of suspending or stabilizing agent. U.S. Pat. No. 5,308,526 to Dias et al and U.S. Pat. No. 5,439,682 to Wivell et al, for example, teach the use of crystalline ethylene glycol long chain esters (e.g., ethylene glycol distearate) as suspension agents to prevent the separation of oil droplets from the liquid. There is no disclosure of a water soluble or water swellable starch in combination with fatty acid as a structuring system to provide enhanced stability.
U.S. Pat. No. 5,518,647 to Zocchi (assigned to Colgate) teaches an emulsion system combining long chain ethoxylated alcohol, free fatty carboxylic acid and water soluble cationic polymer to achieve physical stability of oil droplets in liquid cleanser. There is no teaching or suggestion of using, in specific combination, fatty acid and the starch polymers of the invention.
Another type of well-known suspension agents used to stabilize oil droplets in liquid cleansers are high molecular weight, water-soluble polymers such as polyacrylate, modified celluloses and guar polymers as disclosed broadly, for example, in U.S. Pat. No. 5,661,189 to Grieveson et al. and U.S. Pat. No. 5,854,293 to R. W. Glenn, Jr. (assigned to Procter & Gamble). These polymeric stabilizers are also specifically described, for examples, in U.S. Pat. No. 5,905,062 to Elliott et al. (P&G) claiming hydrophobically modified nonionic cellulose for liquid stability, in U.S. Patent No. 6,172,019 B1 to Dehan et al. (Colgate-Palmolive) using combination of two separate polyacrylic acid polymers and in U.S. Pat. No. 6,001,344 to Villa et al. (Unilever) using the combination of xanthan gum and Carbopol® as a novel structuring system for stable liquid cleansing composition.
Although these polymeric materials are useful for suspending oil droplets in personal liquid cleanser, their thickening/structuring property depends on the liquid cleanser composition, i.e. surfactant type, surfactant level, emollient oil and other additives. As shown in the comparative examples of this invention, these water-soluble polymers tend to separate from the surfactant solution and lose their thickening/structuring property at elevated temperature storage conditions due to incompatibility of these polymeric thickeners with surfactants. To stabilize the liquid cleanser, high level of polymer is required which can in turn cause difficulty in processing and can impart an undesirable lumpy appearance and slimy feel during the use of the product.
Without imparting negative effects on important cleanser properties (such as appearance, lather, in-use/after-use sensory properties and its processability), applicants have found that storage stable liquid cleansers containing emollient oils and/or particles, (e.g., 1 to 30% by wt.) can be formulated using structuring system comprising specific water soluble/or swellable starch polymers combined with linear C8 to C13 fatty acids. Using the polymer/fatty acid structuring system as described in this invention, personal liquid cleansers with non stringy, non lumpy appearance, lotion-like rheology, excellent lather and storage stability can be easily formulated.
Liquid cleansers containing fatty acids are widely described in the art such as in WO 94/17166 to Giret et al, WO 94/18737 to Cothran et al. (P&G), U.S. Pat. No. 5,132,037 to Green et al., U.S. Pat. No. 5,234,619 to Green et al. and U.S. Pat. No. 5,290,470 to Green et al. (Unilever). These patents disclose the use of crystallized fatty acids either as skin benefit agents or as structuring agents. U.S. Pat. No. 5,360,580 to Rizvi et al teach the use of a long chain saturated fatty acid with polyethyleneamine to increase liquid stability. Liquid fatty acids such as oleic acid have been used as structurants to form lamellar structure with specific surfactant composition as described in U.S. Pat. Nos. 5,952,286 and 6,077,816 to Puvvada et al. (Unilever).
Again, none of these prior art references disclose the use of fatty acids of the invention combined with specific water soluble/or swellable starches as efficient structuring system for personal liquid cleansers. Furthermore, as shown in the examples of this invention, some of the fatty acid structured liquid cleanser compositions taught in these prior art references are not stable at elevated temperature especially when the total surfactant level is lower than 20 wt. %, more preferably lower than 15%.
By combining fatty acid and starch polymers, applicants have created a structuring system which provides stable emollient and/or particle containing compositions while at the same time maintaining good consumer desirable properties such as foaming, non-stringiness or non-lumpiness and soft smooth after wash moisturizing skin feel. In a preferred embodiment, this is done at relatively low (equal to or less than 25%, preferably equal to or less than 20%) surfactant levels.